1. Field of the Invention
The present invention relates to a liquid developer imaging system and, more particularly, to a method of developing an image and to a liquid developer imaging system that has a simple structure and uses a high-density developing solution.
2. Description of the Related Art
In a general liquid developer imaging system, light is scanned onto a photosensitive object to form an electrostatic latent image corresponding to a desired image. Next, the obtained electrostatic latent image is developed with a developing solution that is a mixture of powdered toner and a liquid solvent. Then, the developed resultant is printed on paper.
FIG. 1 is a view of an example of a general liquid developer imaging system disclosed in U.S. Pat. No. 5,255,058. Referring to FIG. 1, the general liquid developer imaging system includes: a photosensitive object 10 electrically charged to a predetermined voltage level by a charger 14; an optical scanning device 16 which forms an electrostatic latent image of a desired image by scanning light onto the charged photosensitive object 10 and forming a relative voltage difference thereon; a developing solution supply unit, which supplies developing solution to the photosensitive object 10 to form the electrostatic latent image; and a transferring roller 30 that receives an image developed on the photosensitive object 10 and prints the received image on paper.
The developing solution supply unit generally supplies the developing solution including less than 3% solid toner to the portion between the photosensitive object 10 and a developing roller 38. The developing solution supply unit includes: enriched cartridges 82 and 84 containing enriched developing solution of about 25% solid; a solvent cartridge 86 containing a pure solvent; mixing tanks 55, 57, 59 and 61 that are classified according to colors and mix the developing solution and solvent in the cartridges 82, 84 and 86 to prepare the developing solution of regular concentration, e.g., 2xcx9c3% solid; a supplier 20 for pumping the developing solution prepared in the mixing tanks 55, 57, 59 and 61 by pumps 90, 92, 94 and 96, and supplying the same to the developing roller 38; and a retriever for retrieving the developing solution remaining after the development of an electrostatic latent image. The retriever includes: a collecting container 50 which collects the developing solution remaining after the developing solution is supplied to the developing roller 38 and the photosensitive object 10, and then returns the remaining developing solution to the mixing tanks 55, 57, 59 and 61; a squeezing roller 26, which compresses the photosensitive object 10 where an image is developed and squeezes the developing solution out of the developed image; and a separator 66 for retrieving the squeezed developing solution from the collecting container 50, extracting a toner and a solvent from the developing solution and supplying the extracted solvent to the solvent tank 65.
To develop an image using the above general liquid developer imaging system, four colors of developing solutions containing 2-3% solid, i.e., yellow Y, magenta M, cyan C and black K, are prepared in the mixing tanks 55, 57, 59 and 61, respectively. In the developing system, for a black and white image, only one color developing solution is required, whereas in a liquid developer imaging system, which develops color images, developing solutions of four different colors are needed. To prepare four developing solutions of different colors, the developing solution supply unit extracts enriched developing solution from the enriched cartridges 82 and 84 and a pure solvent from the solvent cartridge 86 and supplies them to the mixing tanks 55, 57, 59 and 61 to prepare developing solutions containing 2xcx9c3% solid. In general, each of the mixing tanks 55, 57, 59 and 61 includes a concentration sensor (not shown) for measuring the concentration of the mixed developing solution. When the developing solutions are prepared, an image is developed as described below.
First, while the photosensitive object 10 is charged with a predetermined electrical charge by the charger 14, light is scanned onto the charged photosensitive object 10 by the optical scanning device 16 and as a result, an electrical potential of the photosensitive object 10 is lowered, thus forming a desired electrostatic latent image. Next, the pumps 90, 92, 94 and 96 are operated to supply the developing solutions from the mixing tanks 55, 57, 59 and 61 to the region between the developing roller 38 and the photosensitive object 10, through the supplier 20, thereby developing the electrostatic latent image. Then, the developed image is transferred onto the transferring roller 30. Next, if the image is composed of one color, then the transferred image is directly printed on paper 72. However, if a desired image is a color image, the above process must be repeated for each respective color, i.e., yellow Y, magenta M, cyan C and black K, so that images developed per color are overlapped on the transferring roller 30 forming a color image. Thereafter, the formed color image is printed on paper 72, which passes all the way through and between the transferring roller 30 and a compressing roller 71.
Such a general liquid developer imaging system is not easy to use because of the complexities in preparing the developing solution, supplying the solution between a developing roller and a photosensitive object, and retrieving it. The complexity in the system is due to the fact that enriched high-density developing solution is not used directly in the general liquid developer imaging system but must be diluted to less than 3% solid by concentration. The use of diluted developing solution makes the fluidity thereof better, thus reducing regional deviation of toner density in a developed image. However, diluting developing solution makes a process of developing an image more complicated. In detail, enriched developing solution and solvent are prepared in each of the enriched cartridges 82, 84 and 86 to be supplied to the mixing tanks 55, 57, 59 and 61, mixed to have a low solid concentration of less than 3% and used to form an electrostatic latent image. Then, the solvent contained in the developed image is squeezed to be retrieved, so that the developing solution has a high concentration to be adapted to print the image. Accordingly, the general liquid developer imaging system becomes larger and more expensive to manufacture. For this reason, there is a growing need for a new liquid developer imaging system to solve this problem.
To solve the above problem, it is an aspect of the present invention to provide an improved liquid developer imaging system in which high-density developing solution can be used without squeezing a solvent from the solution.
Accordingly, to achieve the above aspect, the present invention includes a liquid developer imaging system that has a cartridge for storing a developing solution; a developing container for receiving the developing solution supplied from the cartridge via a predetermined supply line; a developing roller installed for rotating facing a photosensitive object, and partly submerged in the developing solution contained in the developing container; and metering means for scraping off developing solution coated on the surface of the developing roller to a predetermined thickness.
Furthermore, to achieve the above aspect, the present invention includes a method of developing a print image comprising of supplying a developing solution from a cartridge to a developing container by the movement of a piston for compression and expansion of a tube; applying a bias voltage to a development roller, partly submerged in the developing solution contained in the developing container, and to a deposit roller for charging particles of a toner in the developing solution; applying the bias voltage of the deposit roller to a photosensitive object by using a charging roller; scrapping off to a predetermined thickness the developing solution coated on the surface of the developing roller for controlling the concentration of the developing solution; rotating the developing roller facing the photosensitive object for transferring the developing solution onto the photosensitive object for the development of an image; moving a developed image onto a transferring belt without squeezing solvent from the developed image; and printing the image from the transferring table to a medium.